Continuous subcutaneous delivery of medication or monitoring of a body analyte is often accomplished through the use of a cannula, which should remain in place for several days. Diabetes patients may use such a cannula as a subcutaneous compartment for continuous delivery of insulin by pumps or for monitoring interstitial glucose levels by sensors. A combination of a tube, connecting the insulin pump to the cannula and a detachable connector is often referred to as an infusion set. Such infusion sets and modes of their insertion are disclosed, for example, in U.S. Pat. Nos. 4,755,173, 5,176,662 and 5,257,980. Subcutaneous cannula insertion modes for continuous glucose monitoring are disclosed for example in U.S. Pat. Nos. 5,390,671, 5,568,806 and 5,586,553. Usually transcutaneous cannula insertion can be carried out with a sharp metal penetrating member to be withdrawn after skin pricking. This procedure can be effected manually by the patient. The insertion is usually painful and requires considerable skill. Some patients are reluctant or hesitant to pierce their own skin, and thus encounter difficulties in proper cannula insertion. Such difficulties can be attributable to insufficient manual dexterity or alternately to anxiety associated with anticipated discomfort as the needle pierces the skin. This problem can be especially significant when an insulin pump is used since misplacement of the cannula can cause kinking, incorrect insertion angle or incorrect cannula insertion depth leading eventually to cannula obstruction. As a result of this, delivery of insulin may be life threatening.
In an attempt to cope with this problem, automatic infusion set inserters were developed to assure the correct placement of the cannula in the subcutaneous layer, at the correct angle, while minimizing pain and hazardous obstructions associated with cannula insertion. U.S. Pat. Nos. 6,093,172 and 6,830,562 disclose injector devices comprising a spring-loaded plunger for an automatic subcutaneous placement of an infusion set. An automatic cannula insertion is also employed in the skin adhered insulin pump disclosed in U.S. Pat. No. 6,699,218 assigned to Flaherty et al. Unfortunately, this device is relatively bulky, heavy and indiscreet because the spring loaded mechanism is enclosed within the housing during the entire period of usage.
A skin adherable insulin delivery device was disclosed in co-owned U.S. Provisional Patent Application No. 60/837,877. This device includes a unique apparatus for cannula insertion, which does not require an infusion set and long tubing. The cannula insertion apparatus allows the patient to choose the desired depth for cannula insertion and the desired insertion angle. The device is provided with a “well-assembly” connected to the insulin delivery tube. The well assembly has an upper opening and a lower rubber gasket. The insertion apparatus is provided also with a “penetrating cartridge” having a cannula, a penetrating member and a rubber cap. The penetrating cartridge allows for the cannula to penetrate through the well assembly and then through skin, while sealing the upper opening and maintaining the delivery of insulin.
Thus, despite existence of several solutions for cannula insertion, there still exists a need for a device that facilitates cannula insertion within the subcutaneous layer. In particular there is a need for a device for inserting a cannula, which would be suitable for inserting a cannula for delivery of a medication to a patient, by a patch type fluid delivery pump.
There is also a need for a device, which facilitates insertion of a cannula, which would be suitable for continuous analyte monitoring (i.e. continuous glucose monitor).
There is also a need for a device that inserts a cannula at any desired angle.
There is also a need for a device that allows insertion of a cannula at any desired depth.
There is also a need for a cannula insertion device that maintains precise alignment of the cannula relative to the well-assembly. Highly accurate alignment is important for the following reasons:                1. To avoid tearing of the well's lower gasket, thus maintaining intact sealing;        2. To permit skin penetration at a desired angle;        3. To seal of the upper opening with the rubber cap; and        4. For precise placement of the cannula within the well and maintaining flow communication.        
There is also a need for a cannula inserter that can be precisely aligned with the well and subsequently allows pivoting of the well to a desired penetration angle. The inserter itself may serve as a rotating handle which increases the moment applied to the well, thus preventing direct contact between the user's hands and the delicate, sterile, miniature well.
There is also a need for a device that allows manual cannula insertion.
There is also a need for a device that allows automatic cannula insertion.
There is also a need for a cannula insertion device that can be loaded with more than one cannula and thus allows multiple insertions.
In the current disclosure, the device for cannula insertion will be referred to as a cannula inserter or simply as an inserter. In addition, in the current disclosure, the patch type fluid delivery pump will be referred to as the patch.